U.S. patent number 4,513,036 [Application Number 06/542,490] was granted by the patent office on 1985-04-23 for barrier laminates for containment of essential oils and flavors and cartons made therefrom.
This patent grant is currently assigned to Champion International Corporation. Invention is credited to Richard C. Ihde, Kenneth P. Thompson.
United States Patent |
4,513,036 |
Thompson , et al. |
April 23, 1985 |
Barrier laminates for containment of essential oils and flavors and
cartons made therefrom
Abstract
A laminate providing an effective barrier to the migration of
essential oils and/or flavorings, such as d-limonene, therethrough
is provided comprising, from the outer surface to the inner
surface, a paperboard substrate, a web of propylene polymer coated
thereon and a web of olefin polymer overlying said propylene
polymer web. Preferably the paperboard substrate is also coated on
the external surface thereof with a web of heat sealable olefin
polymer. Containers constructed from such laminates are especially
useful as fruit juice containers which enable significant flavor
retention in the fruit juice contained therein over the normal
shelf life of the product.
Inventors: |
Thompson; Kenneth P. (Canton,
NC), Ihde; Richard C. (Strongsville, OH) |
Assignee: |
Champion International
Corporation (Stamford, CT)
|
Family
ID: |
24164038 |
Appl.
No.: |
06/542,490 |
Filed: |
October 17, 1983 |
Current U.S.
Class: |
206/524.6;
428/34.2; 428/354; 428/513; 264/447; 264/483; 264/80; 428/349;
428/516 |
Current CPC
Class: |
B32B
7/12 (20130101); B32B 27/08 (20130101); B32B
27/32 (20130101); B32B 38/0008 (20130101); B32B
27/10 (20130101); B32B 2310/0445 (20130101); Y10T
428/2826 (20150115); B32B 2439/00 (20130101); B32B
2323/10 (20130101); B32B 2310/14 (20130101); Y10T
428/31913 (20150401); B32B 2307/31 (20130101); Y10T
428/2848 (20150115); Y10T 428/31902 (20150401); Y10T
428/1303 (20150115) |
Current International
Class: |
B32B
27/10 (20060101); B32B 027/00 () |
Field of
Search: |
;428/537,507,35,347,349,354,511,353 ;264/22,80 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Lesmes; George F.
Assistant Examiner: Buffalow; E. Rollins
Attorney, Agent or Firm: Sommer; Evelyn M.
Claims
What is claimed is:
1. A container for liquids containing essential oils and/or flavors
constructed from laminate a comprising an outer paperboard layer, a
layer of propylene polymer coated on an inner surface of said
paperboard layer, and propylene polymer layer having an inner
surface which has been treated to enhance adhesion, and a heat
sealable layer of an olefin polymer coated on said treated inner
surface of said propylene polymer layer.
2. The container of claim 1 wherein said inner surface of said
propylene polymer layer has been flame treated to enhance
adhesion.
3. The container of claim 1 wherein said inner surface of said
propylene polymer layer has been corona discharge treated to
enhance adhesion.
4. The container of claim 1 further comprising a layer of adhesive
between said propylene polymer layer and said olefin polymer layer
to bind the latter to the former.
5. The container of claim 4 wherein said adhesive layer is a layer
of ethylene methacrylate.
6. The container of claim 5 wherein said ethylene methacrylate
layer is cross-linked.
7. The container of claim 1 wherein said propylene polymer is
polypropylene and said olefin polymer is polyethylene.
8. The container of claim 1 wherein the outer surface of said
paperboard layer is coated with a layer of a heat sealable olefin
polymer.
9. The container of claim 8 wherein the heat sealable olefin
polymer is polyethylene.
10. The container of claim 9 wherein the heat sealable olefin
polymer is low density polyethylene.
11. A container for liquids containing essential oils and/or
flavors construed from a laminate comprising an outer paperboard
layer, a layer of propylene polymer coated on an inner surface of
said paperboard layer, a layer of ethylene methacrylate polymer
adhesive coated on an inner surface of said propylene polymer
layer, and a layer of olefin polymer coated on an inner surface of
said ethylene methacrylate adhesive layer.
12. The laminate of claim 11 wherein said propylene polymer, said
ethylene methacrylate adhesive, and said olefin polymer layers are
coextruded onto said paperboard layer.
13. The laminate of claim 1 wherein said ethylene methacrylate
layer is cross-linked.
14. The container of claim 11 wherein the outer surface of said
paperboard layer is coated with a layer of heat sealable olefin
polymer.
15. The container of claim 11 wherein the heat sealable olefin
polymer is polyethylene.
16. The container of claim 11 wherein the heat sealable olefin
polymer is low density polyethylene.
17. A process for improving the resistance of paperboard to the
migration of essential oils and/or flavorings therethrough from a
liquid containing such essential oils and/or flavorings, said
process comprising the steps of:
(a) coating an inner surface of said paperboard with a propylene
polymer layer;
(b) treating an inner surface of said propylene polymer layer to
enhance its adhesion;
(c) coating said treated inner surface of said propylene polymer
layer with a heat sealable olefin polymer layer, said olefin
polymer layer being intended to contact the liquid containing the
essential oils and/or flavorings, and
(d) forming the treated paperboard into a container.
18. The process of claim 17 wherein said adhesion enhancing
treating step comprises coating said inner surface of said
propylene polymer layer with an ethylene methacrylate layer.
19. The process of claim 17 wherein said adhesion enhancing step
comprises flame treating of said inner surface of said propylene
polymer layer.
20. The process of claim 17 wherein said adhesion enhancing step
comprises corona discharge treating of said inner surface of said
propylene polymer layer.
21. The process of claim 17 comprising the additional step of
coating the outer surface of said paperboard with a heat sealable
olefin polymer.
22. The process of claim 21 wherein the heat sealable olefin
polymer is polyethylene.
23. The process of claim 21 wherein the heat sealable olefin
polymer is low density polyethylene.
24. A process for improving the resistance of paperboard to the
migration of essential oils and/or flavorings therethrough from a
liquid containing such essential oils and/or flavorings, said
process comprising coextruding a tripartite layer onto said
paperboard, said tripartite layer including a component layer of a
propylene polymer contacting an inner surface of said paperboard,
an intermediate layer of ethylene methacrylate polymer, and an
inner heat sealable layer of olefin polymer, and forming the
treated paperboard into a container.
Description
This invention relates to barrier laminates for the containment of
essential oils and flavors and cartons made therefrom. More
particularly, this invention relates to barrier laminates useful in
cartons which hold liquids containing essential oils and flavorings
such as fruit juices.
For many years, taste and flavor experts have been quite critical
of the standard polyethylene coated paperboard containers currently
on the market because the essential oils and flavoring contained in
fruit juices can diffuse through the polyethylene coating itself to
deposit in the paperboard thereby downgrading the initial flavor of
the fruit juice in a very marked manner during its standard shelf
life.
While the migration of the essential oils and flavorings could be
substantially reduced by the use of a laminate containing a metal
foil therein mounted as a liner along the interior of the
container, the economics involved in using a metal foil preclude
this solution from being a viable alternative. Despite the fact
that many attempts have heretofore been made to enable the
replacement of metallic foil with a polymeric laminate which would
enable flavor retention throughout the standard shelf life at a
relatively low cost, all such efforts to date have substantially
failed to come up with a resonable substitute for metal foil.
Now, in accordance with the present invention, it has been found
that a laminate providing a substantial barrier to the migration of
essential oils and/or flavors therethrough is achieved by a
laminate comprising, from the outer surface to the inner surface
contacting said essential oils and/or flavors: a paperboard
substrate, a web of propylene polymer coated thereon and a web of
olefin polymer overlying said propylene polymer web and rendering
the resulting laminate heat-sealable. It has been found that
cartons constructed of the laminate of the present invention enable
significant flavor retention of the fruit juice contained therein
resulting in a significant extension of the shelf life thereof and
permit the replacement of an otherwise required aluminum foil
barrier at considerable economic savings.
In the container field, it has been common practice to use many
forms of materials which are heat-sealed or glued and otherwise
converted on conventional equipment to form a container or carton.
Such containers are those typically known in the trade as "folding
boxes", containers or cartons.
By way of example, one such carton is the gable-top milk carton and
carton blanks therefor which are specifically disclosed in U.S.
Pat. No. 3,120,333 as liquid-tight containers. Essentially, blanks
used in the manufacture of such containers include a paperboard
base, extrusion coated on both sides with a resin, such as
polyethylene, to provide a moisture barrier and to provide means
for heat-sealing the carton.
In a typical carton converting operation, once the resin-blanks are
cut and scored, the resin on an outer surface of a glue flap and
the resin on an inner surface of a carton panel are heated by
direct flame application while the heated carton surfaces extend in
guided but essentially unsupported, i.e., not compressed between
two heating jaws, condition over the edges of a conveying belt. The
carton panels are then folded over to form a a flattened tube, the
now molten tacky resin on the heated surfaces are pressed together
at a down-stream nip to form as liquid-tight side seam. The
cartons, in a flattened tube form, are then shipped to users such
as dairies or juice manufacturers where they are finally erected by
further heat-sealing, filled and finally sealed.
While these familiar gable-top cartons have been extensively used
throughout the United States to contain milk or juices, they are
associated with some problems. One such problem results from
wetting of the paperboard component of the carton. Pinholing of the
resin and film failure or creasing along fold lines are examples of
other problem areas where wetting is likely to occur. Moisture is
also "wicked", or drawn by capillary action into the paperboard via
the exposed paperboard at the edge of the glue flap which resides
within the filled carton. Moreover, certain essential oils and/or
flavorings, generally found in fruit juices, e.g. apple juice,
cranberry juice, grape juice, orange juice, and the like possess
the capability of migrating through the polyethylene moisture
barrier into the paperboard with resulting loss in flavor of the
fruit juice over the normal shelf life.
Many attempts have heretofore been made to overcome the problems of
wetting of the paperboard or diffusion of essentil oils through the
polyethylene moisture barrier with resultant loss in flavor. One
attempt involves the use of a liner for the internal surface of the
container comprising a laminate having two or more laminae of
polyolefin or other polymeric material sandwiching a metallic foil
therebetween. The presence of the metallic foil significantly
reduces both moisture transmission and loss of essential oils to
the paperboard. The use of metallic foil, however, complicates
processing and significantly increases the cost of the resulting
product. Other attempts at overcoming these problems have resulted
in the suggestion to use homogeneous, all plastic containers such
as can be formed by a blowmolding operation. By virtue of the fact
that these containers are completely formed and that their
transportation thus includes transporting the air in them, shipping
charges are substantially increased over shipping charges for
similar volume containers which can be shipped in a flattened
condition. Moreover, such containers are not readily adaptable to
inexpensive printed decorations.
All-plastic carbon blanks cut and scored in patterns similar to
those of the resin-coated paperboard cartons described hereinabove
have also been developed. However, when these plastic containers
are run through a typical resin-coated paperboard converter, extra
attention and care has to be taken with the side-seaming by direct
flame application to the unconfined container surfaces.
Thus, while homogeneous all-plastic blanks could possibly be sealed
by some known heat-sealing technique such as a static system
wherein the heated areas are supported or confined, for example,
between heating jaws, no such other known techniques are capable of
high commercial production speed. Moreover, the use of other
sealing techniques would require the converter to purchase other
equipment to provide efficient sealing of the all-plastic container
rendering the currently available equipment obsolete. Accordingly,
such all-plastic containers have not been commercially accepted to
any significant degree.
Thus, until the advent of the present invention no suitable
containers for the containment of fruit juices have been developed
which retain the advantages of using paperboard as the base
material and yet eliminate both the processing and economic
disadvantages of the use of metal foil.
The advantages of the present invention will become more readily
apparent from the following detailed description and drawing in
which:
FIG. 1 is a cross-sectional elevation of one embodiment of the
laminate of the present invention; and
FIG. 2 is a cross-sectional elevation of an alternate embodiment of
the laminate of the present invention.
The invention described herein is particularly useful as a
paperboard laminate employed in the manufacture, for example, of
containers of many various types. Such containers, for example, may
comprise folding boxes, square or rectangular containers or
cartons, or simply cylindrical tubes having a bottom closure means
and generally also a top closure means.
For example only, one particular form of container configuration
with which the present invention is highly useful is the gable-top
carton for the containment of liquids described, for example, in
U.S. Pat. No. 3,120,333.
Referring now to FIG. 1, the laminate of the present invention is
shown as comprising a paperboard substrate 10 which is most
suitably high-grade paperboard stock, for example 0.010 to 0.028
milk carton stock, to which is applied a web of propylene polymer
12 in a coating weight ranging from about 5 to about 20 pounds per
ream. Any propylene polymer is currently believed suitable for use
herein, for example, polypropylene homopolymer, copolymers of
propylene and other olefins copolymerizable therewith wherein the
propylene constitutes at least about 75% by weight of the copolymer
as well as other modified propylene polymers can be suitably
employed. Most preferably, an extrusion coating grade polypropylene
is employed. Typical of such suitable extrusion coating grade
polypropylene are Gulf polypropylene 7914 and 7917 available from
Gulf Oil Chemicals Company, Orange, Tex.
Overlying said polypropylene web 12 is a web of heat-sealable
olefin polymer 14. Preferably, the olefin polymer is polyethylene
and most preferably, a low density polyethylene. Typical of the
preferred low density polyethylenes which can be employed as web 14
is Gulf 4517 polyethylene available from Gulf Oil Chemicals
Company, Houston, Tex. The olefin polymer web 14 is applied in a
coating weight ranging from about 5 to about 20 pounds per ream.
The relative coating weights of the propylene polymers to olefin
polymer webs should range from about 50:50 to about 75:25.
Referring now to FIG. 2, wherein like numerals with a prime (')
designation designate laminae of the same type described in FIG. 1,
an alternate embodiment of a laminate of the present invention is
shown. In this alternate embodiment, the paperboard substrate 10'
is coated on the external surface thereof with a web of
heat-sealable olefin polymer 16', typically polyethylene and most
preferably, low density polyethylene. This external coating of
olefin polymer imparts heat-sealability to the ultimate container
construction and also imparts a gloss to the external surface of
the paperboard which, with suitable, yet conventional treatment,
can be directly printed upon. On the internal surface of the
paperboard substrate 10' is applied a web of propylene polymer 12'
as described hereinabove. Overlying the propylene polymer web is a
web 14' of heat-sealable olefin polymer which will ultimately form
the internal surface of the container constructed therefrom.
To enhance the adhesion between the olefin polymer web 14' and the
propylene polymer web 12', an adhesive layer 18 can be interposed
therebetween. Although any suitable adhesive can be employed, it
has been found that a copolymer of ethylene and methacrylic acid
(EMA) is especially suitable. It has been found especially
desirable, when employing EMA, to expose the resulting laminate to
electron beam radiation in a dosage of about 10 megarads in order
to cross-link the EMA and enhance the bondbetween the olefin
polymer layer 14' and the propylene polymer barrier layer 12'.
The laminates of the present invention can be easily fabricated.
For example, the propylene polymer and olefin polymer webs can be
directly coextruded onto the paperboard substrate. Alternatively,
in order to facilitate adhesion between the propylene polymer and
the olefin polymer, a layer of EMA can be simultaneously coextruded
between the propylene polymer and olefin polymer webs as they are
directly coextruded onto the paperboard substrate. Still further,
if desired, a two-pass coating operation can be employed whereby
the propylene polymer web is extruded onto the paperboard substrate
and, if desired, the resulting propylene polymer coated paperboard
can be treated by flame treatment, corona discharge, or the like to
enhance adhesion, and subsequently overcoating the propylene
polymer barrier web with a web of olefin polymer.
Although these specific coating techniques have been described, it
is apparent to those skilled in the art that any conventional
technique for applying the propylene polymer and olefin polymer
webs to a paperboard substrate can be suitably employed.
The unique barrier effect provided by the laminate of the present
invention to the transmission of essential oils and flavorings is
clearly demonstrated by the following comparative example.
Standard paperboard 1/2 gallon orange juice containers were
prepared and filled with orange juice. The principle essential oil
in orange juice is d-limonene. The filled cartons were stored for a
period of six weeks after which time the orange juice was analyzed
to determine the percentage loss by weight of the essential oil
d-limonene and the percentage loss by weight of vitamin C.
The standard 1/2 gallon orange juice container was constructed from
a laminate consisting (from the outside of the container in) of 7.8
pounds per ream polyethylene, 0.024 milk carton stock and 20 pounds
per ream polyethylene.
Another standard paperboard 1/2 gallon orange juice container was
modified to contain an aluminum foil lining. The structure from the
outside of the container in was 7.8 pounds per ream low density
polyethylene, 0.024 milk carton stock, 10 pounds per ream low
density polyethylene, 0.00035" aluminum foil and 20 pounds per ream
low-density polyethylene.
A third comparative container was prepared by modifying the
standard paperboard 1/2 gallon orange juice container to contain a
high density polyethylene lining. The structure of this carton from
the outside in was 7.8 pounds per ream low density polyethylene,
0.024 milk carton stock, 10 pounds per ream high density
polyethylene and 10 pounds per ream low density polyethylene.
Finally, a standard paperboard 1/2 gallon orange juice container
was prepared from the laminate of the present invention comprising
from the outside of the container in 7.8 pounds per ream
polyethylene, 0.024 milk carton stock, 10 pounds per ream of
extrusion coating grade polypropylene and 10 pounds per ream low
density polyethylene.
Table I set forth below sets forth the results of the shelf storage
life tests after the six week storage period.
TABLE I ______________________________________ % Loss of % Loss of
Test Sample Essential Oil Vitamin C
______________________________________ Standard paperboard 60.5 84
1/2 gallon orange juice container (polyethylene- paperboard -
polyethylene) Standard paperboard 35.5 24 1/2 gallon orange juice
container modified to con- tain aluminum foil lining
(polyethylene-paperboard- polyethylene-aluminum foil- polyethylene)
Standard paperboard 60.5 87 1/2 gallon orange juice con- tainer
modified to contain a high density polyethylene lining
(polyethylene-paperboard- 10#/ream high density poly-
ethylene-10#/ream low density polyethylene) Standard paperboard 1/2
39.5 71 gallon orange juice container constructed from the laminate
of the present invention (poly- ethylene-paperboard-10#/ream
polypropylene-10#/ream polyethylene)
______________________________________
It can be clearly seen that the container prepared from a laminate
of the present invention provided substantially the same barrier to
the d-limonene as did the laminate containing the aluminum foil.
The container formed from the laminate of the present invention,
while not providing as good a barrier to vitamin C as that provided
by the container having an aluminum foil liner, nevertheless,
provided a better barrier against vitamin C loss than has
heretofore been obtainable in the absence of the use of a metal
foil liner.
The effectiveness of the laminate of the present invention as a
barrier to the migration of essential oils the flavors permits a
significant extension of the shelf life of containers constructed
therefrom and permits the replacement of an aluminum foil barrier
in such containers with resultant significant economic savings.
* * * * *